The objectives of this contract are to determine the in vitro affinity and intrinsic activity of test compounds at multiple receptor targets to support both the cocaine and opiate treatment discovery programs. For compounds of interest to the Cocaine Treatment discovery Program (CTDP), compound activity will be evaluated at multiple dopamine and serotonin receptor subtypes, and for compounds of interest to the Opiate Treatment discovery Program (OTDP), compounds activity will be valuated at multiple opioid receptors. Complete reports of these in vitro activities will be provided to the Project Officer for use in compound characterization and advancement to further testing within the discovery programs. Copies of these reports which include data and methodologies will also be distributed to compound submitters. In addition to compound testing and throughout the life of the contract, new receptor assays for binding and functional activity will be established, validated, and integrated into the screening programs as directed by the Project officer. New assay development for receptor binding and functional activity will not necessarily be limited to dopamine, serotonin or opioid receptors.